Temperature control device



March 21, 1939. J. 1.. FINCH TEMPERATURE CONTROL DEVICE 2 Sheets-Sheet l Filed Feb. 10, 1956 INVENTOR. JAMES LESLIE FINCH ATTORNEY.

March 21, 1939. J. FINCH TEMPERATURE CONTROL DEVICE Filed Feb. 10, 1956 2 Sheets-Sheet 2 INVENTOR JAMES LESLIE FINCH uuuumuu ATTORNEY. v

UNITED STATES PATENT OFFICE TEMPERATURE CONTROL DEVICE James Leslie Finch, Patchoguc, N. Y., assignor to Radio Corporation of America, a corporation of Delaware Application February 10, 1936, Serial No. 63,145

This invention relates to a novel and improved 5 Claims.

temperature control device.

More specifically, this invention relates to a specific type of temperature control device for 5 maintaining exceedingly constant temperature and providing convenient means of extremely fine and accurate adjustment.

An object of this invention is to provide an extremely accurate temperature control device which is substantially constant and reliable in operation over a long period.

Another object of this invention is to provide a temperature control device having a plurality of contact adjustable means which are located external of the container.

A feature of this invention is the employment .of the principle of differential expansion with increase in temperature of two different materials. It employs in principle the use of a container for the medium whose temperature is to be controlled to form one portion of the thermostat element. It

also conceives the use of a principle similar to that employed in a hot wire meter for multiplying a small motion in order to geta larger motion at the point where a contact is to be made or broken.

ligible.

Likewise, temperature control devices of, the prior art are subject to non-uniformity of temperature within the device. For example, the upper portions are often very materially warmer than the lower portions.

One of the features of this invention is to maintain the walls on all sides of the container at a substantially constant and equal temperature.

This results in all points within the container being maintained at con-,

stant equal temperature unless heat is liberated Within it.

Many forms of temperature control devices known in the prior art have been found very difficult to change the temperature held by the control element. This invention makes it very simple to change the temperature and to maintain it substantially constant over a relatively long period. Furthermore, in inventions in the prior 7 art it was necessary to provide a heavy metallic container inside the control device for smoothing out the temperature variations caused by the cycles mentioned above.

This invention elimi- Figure 2 is a detail of the linkage system of this invention,

Figure 3 is a detail of a modification in a heater arrangement,

Figure 4 is a detailed modification of the improved contact arrangement,

Figure 5 is a modification of the linkage system.

Referring now to Figure 1, a box I serving as' a container for the device to be controlled, surrounds the device whose temperature is to be controlled such as, for example, a piezo-electric crystal. Heat is supplied to the container by passing an electric current through the resistance wire 2 embedded in the walls of container I. This current is supplied by the source 3 through the relay contacts 4 which are connected in series with the heater wires 2 and a contact within the container. It is desirable that the wires 2 be in intimate contact with the container walls in order that the best results may be obtained. The amount of heat liberated in the walls of the container in any given portion should be equal to the heat required to maintain that portion at the desired operating temperature. Also, for efficient results the conductivity of the container should be relatively high to allow the heat liberated by resistance wire 2 to flow from areas where the heat liberated is in excess to that required in areas where the heat liberated is lower than that required without resulting in any appreciable change within the temperature of the container. The control of the heating is maintained by having located within container I, a set of linkage members 6, 1, 8, 9, Lil, and [2. These linkage members are supported by the container I at or near the intersecting points of the central lines of the faces of the container. The junction point between link members I and 8 is arranged to be pulled out of line with a spring l3. At this point of junction, a contact I4 is placed which is electrically insulated from the links I and 8. An adjustable stationary contact or screw i5 is maintained in the container l and is insulated therefrom by an insulating bushing 30. Link members 6, l, 8, 9, l0 and II are preferably made of material having a very low temperature coefllcient of expansion, it being desirable that their coeflicient of expansion be substantially zero. The container on the other hand is made of material with a relatively high temperature coeflicient of expansion, as the fundamental principle of this invention resides in that when the temperature of the container and all other elements within the container rises, the container will expand in a ratio which is greater than'that of the links. This relative motion will cause contact I4 to be drawn toward the stationary contact I5 which motion will be resisted by spring I3. The position of contact screw I5 is so adjusted relative to contact I4 that contacts l4 and I5 make connection at the temperature which is desired to be maintained within the container. The initial tension in the spring I3 is so adjusted with relation to the tension which links 6, I, 8, 9 will stand that the contacts I4 and I5 will be moving at the maximum rate per degree of temperature change at the time when they make contact.

Referring to the linkage system I2 which consists of a number of component parts such as a lever I6, one end of which is secured to the container I by means of nut II, screw I8 and shoulders I9, the link 9 is secured to lever I6 very close to the end where it is held by the adjustable support member IT. This provides a leverage such that when a small force is applied at the left hand end of lever I6, there will be produced a relatively large force in link 9. Conversely, any motion at the end of lever I6 will be reduced greatly in respect to the resultant motion at the end oi! link 9. A lever 20 is attached to lever I6 at its right hand end. An electrical contact 2| is maintained near the middle of lever 20. A spring 23 draws contact 2| against contact 22 which is maintained on the left hand end of IS. The left hand end of lever 2|) is secured to the container I by means of a screw 24 and shoulder 25. The spring member 23 has an initial tension greater than that required to hold 2| and 22 in contact for any tension in the links 6, I, 8, 9, less than that required to make contact between members I4 and I5. The contacts 2| and 22 are connected in an electrical circuit of the heater wire 2 so that when they are opened no heat will be generated. These contacts are provided so that in case relay contacts 4 should not open as required, or if the temperature of I should increase beyond the desired value, contacts 2| and 22 will open, thus preventing excess of temperature rise, as any excess temperature rise would produce excessive strains in links 6, I, 8, 9 and might deform them permanently.

The nonnal operation of this device is as follows:

When the temperature falls below that desired, contacts l4 and, I5 will be separated. This opens the circuit from voltage source 3 through relay windings 5 which allows the armature of relay to drop and make contacts 4 close. Contacts 2| and 22 are also closed. Thus, the circuit is completed from the source of supply through contacts 4 to 2| and 22 so that heat will be generated in the wire 2. This heat causes the temperature of the container I to rise and thus increase the temperature so that contacts I4 and I5 will close when the desired temperature is reached. This rise 01' temperature causes relay winding 5 to be energized thus raising the armature, opening relay contacts 4 and preventing further heat from being liberated in container The temperature will then fall due to heat being carried away from the container I and the circuit through contacts I4 and I5 is opened again causing relay contacts 4 to close again and thus repeat the cycle. The opening and closing of contacts 4 are indefinitely repeated thus maintaining the desired temperature. Should it be desired to change the temperature from that previously being held, a rough adjustment can be made by turning screw I8 and a still finer adjustment can be made by turning screw 24.

In the detailed modification shown in Figure 3, the heater wires are generally similar to those of Figure 1 except that the heater ,Wire 2 is located on the outside of container I and wound upon a card 3| of insulating material which is pressed against container I and held in this position by any suitable means such as clamps 32.

The modified contact arrangement shown in Figure 4 is in all respects similar to the arrangement shown in Figure 1 except that contacts I4 and I5 are placed at the end of a lever which is so arranged that the motion at the junction point between members 1 and 8 is amplifled by the additional lever.

In the modified linkage system shown by Figure 5 the device is made more sensitive by the addition of links to 44 inclusive and are arranged to continue around the container in any desired number of times before finally terminating in the thermostat mechanism |2.

It will be obvious to those skilled in the art that heat control can be effected by other means than those shown in the drawings, therefore this invention should not be limited to the modification shown except such limitations that are clearly imposed by the appended claims.

I claim:

1. A temperature control device comprising a rectangular container, said container acting as one element of a regulating thermostat, the other element of said regulating thermostat comprising a plurality of linkages secured to each corner of said container and having relatively low temperature coefficient of expansion compared with that of said container.

2. A temperature control device comprising a container, said container acting as one element of a regulating thermostat, the other element of said regulating thermostat comprising a plurality of linkages located within said container and extending around the interior of the surface of said container several times.

3. A temperature regulating device comprising a rectangular container having a plurality of heater wires embedded in the walls thereof and equally spaced to distribute the heating equally throughout, said container acting as one element of a thermostat device, the other element of said thermostat device comprising at least three links located at each corner and within said container.

4. A temperature control device as in claim 3, having said heater wires cast within the walls oi. the container.

5. A temperature regulating device comprising a container, the walls of said container acting as at least one element of a thermostat, the other elements of the thermostat comprising a plurality of links, an electrical contact mounted on at least one of said links for actuating relay contacts for controlling an external electrical circuit for heating said container, and a second contact located at the end of another one of said links and electrically connected in series with said relay contacts.

JAMES LESLIE FINCH. 

